Method of measuring aerial image of EUV mask

ABSTRACT

An apparatus for measuring an image of a pattern to be formed on a semiconductor by scanning the pattern using a scanner, the apparatus including an EUV mask including the pattern, a zoneplate lens on a first side of the EUV mask and adapted to focus EUV light on a portion of the EUV mask at a same angle as an angle at which the scanner will be disposed with respect to a normal line of the EUV mask, and a detector arranged on another side of the EUV mask and adapted to sense energy of the EUV light from the EUV mask, wherein NA zoneplate =NA scanner /n and NA detector =NA scanner /n*σ, where NA zoneplate  denotes a NA of the zoneplate lens, NA detector  denotes a NA of the detector, and NA scanner  denotes a NA of the scanner, σ denotes an off-axis degree of the scanner, and n denotes a reduction magnification of the scanner.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application based on pending application Ser. No.12/910,605, filed Oct. 22, 2010, which in turn is a continuation ofapplication Ser. No. 12/659,261, filed Mar. 2, 2010, now U.S. Pat. No.7,821,714 B1, the entire contents of which is hereby incorporated byreference.

BACKGROUND

1. Field

Embodiments relate to a method of manufacturing a semiconductor device.More particularly, embodiments relate to an apparatus and a method ofmeasuring a defect of a mask used to form a fine pattern during ascanning process employable during manufacturing a semiconductor device.

2. Description of the Related Art

Recently, as illumination light sources having shorter wavelengths areneeded to further miniaturize the line width of a semiconductor circuit,research into a scanning process using an extreme ultra-violet (EUV)having a wavelength of 50 nm or less as a scanning light source has beenactively performed.

Since the complexity of a scanning process has gradually increased, evena small defect in a mask may cause a serious defect in a circuit patternon a wafer. Thus, when a pattern is formed on a wafer by using aphotomask, in order to identify in advance the influence of variousdefects formed in the photomask on the wafer, defects of the photomaskare detected by measuring the aerial image of the photomask.

A conventional apparatus for measuring an aerial image of a EUV maskincludes a plurality of EUV mirrors. Thus, the manufacture andinstallation of the mirrors require use of various technologies. Inaddition, many mirrors are used because the reflection rate of onemirror is not 100%. Thus, a high power source is required. Accordingly,such conventional apparatus for measuring an aerial image of a EUV maskis expensive, and additionally, a long development period is necessaryfor making the apparatus.

SUMMARY

Embodiments are therefore directed to an apparatus for and a method ofmeasuring a defect in a mask, which substantially overcome one or moreof the problems due to the limitations and disadvantages of the relatedart.

It is therefore a feature of an embodiment to provide an apparatus forand a method of measuring a defect in a mask employable for forming afine pattern during a scanning process employable during manufacturing asemiconductor device.

It is therefore another feature of an embodiment to provide an apparatusfor measuring an aerial image of an extreme ultra-violet (EUV) mask,wherein the apparatus is capable of perfectly emulating a numericalaperture (NA) and off-axis degree (σ) of a scanner although the overallcomplexity and required technological level thereof may be simplifiedand/or reduced as compared to comparable conventional devices.

It is therefore a separate feature of an embodiment to provide anapparatus for measuring an aerial image of a EUV mask, wherein theapparatus may have a shorter development period and/or lower developmentcost than a comparable conventional apparatus for measuring an aerialimage of a EUV mask.

At least one of the above and other features and advantages may berealized by providing an apparatus for measuring an aerial image, theapparatus including a movable unit adapted to move a reflective extremeultra-violet (EUV) mask disposed thereon in an x-axis and/or y-axisdirection, an X-ray mirror arranged on the movable unit, the X-raymirror being adapted to selectively reflect a coherent EUV light havinga selected wavelength, a zoneplate lens that is located between themovable unit and the X-ray mirror, the zoneplate lens being adapted tofocus the coherent EUV light on a portion of the reflective EUV mask,and a detector arranged on the movable unit, the detector being adaptedto sense energy of the reflected coherent EUV light when the focusedcoherent EUV light is reflected by the portion of the reflective EUVmask, wherein NA_(zoneplate)=NA_(scanner)/4 andNA_(detector)=NA_(scanner)/4*σ, where NA_(zoneplate) denotes a numericalaperture (NA) of the zoneplate lens, NA_(detector) denotes a NA of thedetector, and NA_(scanner) denotes a NA of a scanner, and σ denotes anoff-axis degree of the scanner.

An aperture may be between the reflective EUV mask and the detector.

The X-ray mirror may include a multi-layer structure including at leastone molybdenum layer and at least one silicon layer, which arealternately arranged.

The EUV light generator may include a high power femtosecond laseradapted to output a high power femtosecond laser beam, a gas celladapted to generate the coherent EUV light having a selected wavelengthfrom the high power femtosecond laser, and a lens adapted to focus thehigh power femtosecond laser beam on the gas cell.

The gas cell may be filled with a neon gas so as to optimize aproduction efficiency of a coherent EUV light having a wavelength of13.5 nm.

The X-ray mirror may be adapted to reflect the coherent EUV lightemitted from the EUV light generator toward the portion of thereflective EUV mask at an angle of about 4° to about 8° with respect toa normal line of the reflective EUV mask.

The zoneplate lens may be adapted to focus the reflected coherent EUVlight on the portion of the reflective EUV mask at an angle of about 4°to about 8° with respect to a normal line of the reflective EUV mask.

The apparatus may include a computing unit adapted to reconstruct animage of the reflective EUV mask based on energy sensed by the detector.

At least one of the above and other features and advantages may beseparately realized by providing an apparatus for measuring an aerialimage of a pattern corresponding to a semiconductor pattern to be formedby scanning the pattern using a scanner, the apparatus including anextreme ultra-violet (EUV) mask including the pattern, a zoneplate lensarranged on a first side of the EUV mask and adapted to focus EUV lighton a portion of the EUV mask at a same angle as an angle at which thescanner will be disposed with respect to a normal line of the EUV mask,and a detector arranged on a second side of the EUV mask and adapted tosense energy of the EUV light from the EUV mask, whereinNA_(zoneplate)=NA_(scanner)/n and NA_(detector)=NA_(scanner)/n*σ, whereNA_(zoneplate) denotes a NA of the zoneplate lens, NA_(detector) denotesa NA of the detector, and NA_(scanner) denotes a NA of the scanner, σdenotes an off-axis degree of the scanner, and n denotes a reductionmagnification of the scanner.

The apparatus may include a movable unit on which the EUV mask isarranged, the movable unit being adapted to move the EUV mask in anx-axis direction and/or an y-axis direction.

The EUV mask may be a reflective EUV mask including a reflectivematerial.

The detector may be adapted to sense energy of reflected EUV light thatis reflected from the reflective EUV mask.

The apparatus may include an EUV light generator and an X-ray mirroradapted to selectively reflect the EUV light from the EUV lightgenerator.

The EUV light generator may include a high power femtosecond laser.

The EUV mask may be a transmissive EUV mask.

The detector may be adapted to sense energy of transmitted coherent EUVlight that is transmitted through the transmissive EUV mask.

At least one of the above and other features and advantages may beseparately realized by providing a method of measuring an aerial imageof a pattern corresponding to a semiconductor pattern to be formed byscanning the pattern using a scanner, the method including generatingextreme ultra-violet (EUV) light, reflecting the generated EUV lightusing an X-ray mirror, transmitting the reflected EUV light from theX-ray mirror using a zoneplate lens toward the pattern on an EUV mask,sensing energy of the EUV light from the EUV mask using a detector,converting the sensed energy into image information and storing theimage information, moving the EUV mask in an x-axis direction and/or ay-axis direction, and outputting the aerial image of the pattern of theEUV mask based on the stored image information, whereinNA_(zoneplate)=NA_(scanner)/4 and NA_(detector)=NA_(scanner)/4*σ, whereNA_(zoneplate) denotes a numerical aperture (NA) of the zoneplate lens,NA_(detector) denotes a NA of the detector, and NA_(scanner) denotes aNA of a scanner, and σ denotes an off-axis degree of the scanner.

Generating extreme ultra-violet (EUV) light may include generating ahigh power femtosecond laser beam.

Reflecting the generated EUV light using an X-ray mirror may includereflecting the EUV light emitted from an EUV light generator toward aportion of the EUV mask at an angle of about 4° to about 8° with respectto a normal line of the EUV mask.

Transmitting the reflected EUV light from the X-ray mirror using azoneplate lens may include transmitting the EUV light reflected from theX-ray mirror toward a portion of the EUV mask at an angle of about 4° toabout 8° with respect to a normal line of the EUV mask.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages will become more apparent tothose of ordinary skill in the art by describing in detail exemplaryembodiments with reference to the attached drawings, in which:

FIGS. 1 and 2 illustrate schematic diagrams of an exemplary embodimentof an apparatus employable for measuring an aerial image;

FIG. 3A illustrates a schematic diagram of an exemplary embodiment of azoneplate lens and a detector employable in an apparatus for measuringan aerial image;

FIG. 3B illustrates a schematic diagram of an exemplary embodiment of ascanner employable in an apparatus for measuring an aerial image;

FIG. 4A illustrates a schematic diagram of an exemplary embodiment of acomputing unit employable in an apparatus for measuring an aerial image;

FIG. 4B illustrates a schematic diagram of an exemplary embodiment of adriving process of a detector and a computing unit employable in anapparatus for measuring an aerial image;

FIG. 5 illustrates a perspective view of an exemplary embodiment of amask including a mask pattern and a defect thereon;

FIG. 6 illustrates an exemplary output image corresponding an aerialimage of the mask of FIG. 5, which may be output by the output unit ofFIG. 4B in the form of light and darkness;

FIG. 7 illustrates exemplary cross-sectional aerial images of diagramsthat may be output by the output unit of FIG. 4B, wherein thecross-sections are taken along lines a-a′, b-b′, and c-c′ of FIG. 5;

FIGS. 8A and 8B each illustrate a cross-sectional view of an imageprojected onto a photoresist and a corresponding aerial imagereconstructed by the output unit of FIG. 4B;

FIG. 9A illustrates an exemplary mask pattern that includes a defect andfrom which energy information may be obtained and supplied to the outputunit of FIG. 4B;

FIGS. 9B and 9C respectively illustrate exemplary light and dark aerialimages, which may be output from the output unit of FIG. 4B based on themask pattern of FIG. 9A; and

FIG. 10 illustrates a flowchart of an exemplary embodiment of a methodof measuring an aerial image.

DETAILED DESCRIPTION

Korean Patent Application No. 10-2009-0049097, filed on Jun. 3, 2009, inthe Korean Intellectual Property Office, and entitled: “Apparatus andMethod for Measuring Aerial Image of EUV Mask,” is incorporated byreference herein in its entirety.

Exemplary embodiments will now be described more fully hereinafter withreference to the accompanying drawings; however, they may be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art.

FIGS. 1 and 2 illustrate schematic diagrams of an exemplary embodimentof an apparatus employable for measuring an aerial image.

Referring to FIG. 1, the apparatus for measuring an aerial image mayinclude a reflective extreme ultra-violet (EUV) light generation unit10, an X-ray mirror 20, a zoneplate lens 30, a reflective EUV mask 40(hereinafter referred to as a “mask”), a detector 50, and a computingunit 60. The EUV light generation unit 10 may generate EUV light havinga wavelength about 12 nm to about 14 nm. The EUV light may be coherentEUV light.

The EUV light may be reflected by the X-ray mirror 20 and may movetoward the zoneplate lens 30. The X-ray mirror 20 may selectivelyreflect the EUV light having a wavelength of about 12 nm to about 14 nm.The reflected EUV light may be focused on a portion 45 of the mask 40through the zoneplate lens 30. The EUV light focused on the portion 45may be reflected to the detector 50 by the mask 40. The detector 50 maysense energy of the EUV light and may transfer energy information to thecomputing unit 60.

The X-ray mirror 20 may include palladium (Pd)/carbon (C) and molybdenum(Mo)/silicon (Si). In some embodiments, the X-ray mirror 20 may include,e.g., a Mo/Si multi-layer structure including 80 Mo and Si layers,wherein the Mo layers and Si layers may be alternately formed. The Molayers and the Si layers may be thin films formed by sputtering. TheX-ray mirror 20 may selectively reflect EUV light having a wavelength ofabout 13.5 nm.

The mask 40 may include a reflective material. The mask 40 may includean upper portion with a fine circuit pattern having a size of about 45nm or less.

The apparatus for measuring an aerial image may further include anaperture 46 for transmitting the EUV light reflected by the mask 40. Theaperture 46 may include pinholes 47. A numerical aperture of thezoneplate lens 30 may be controlled by changing a hole size of thepinholes 47.

Referring to FIG. 2, the EUV light generation unit 10 may include alight source 11, a lens 12, and a gas cell 13. The light source 11 maygenerate a high power femtosecond laser beam. The high power femtosecondlaser may be a Ti:Sapphire laser outputting a wavelength of about 800 nmand may be focused on the gas cell 13 through the lens 12. The gas cell13 may be evacuated and may include fine pores for allowing a laser topass therethrough. The gas cell 13 may be filled with neon gas toimprove and/or optimize generation efficiency of the EUV light with awavelength of 13.5 nm.

The X-ray mirror 20 may be arranged such that the generated EUV lightmay be incident on the portion 45 of the mask 40 at a same angle as anincident angle at which a scanner is disposed with respect to a normalline of the mask 40. The zoneplate lens 30 (see FIG. 1) may perform asame function as the X-ray mirror 20. That is, the zoneplate lens 30 maybe arranged such that the EUV light reflected by the X-ray mirror 20 maybe incident on the portion 45 of the mask 40 at the same angle as theincident angle at which a scanner may be disposed with respect to anormal line of the mask 40.

In some embodiments, the incident angle of the scanner may be in a rangeof about 4° to about 8°, e.g., 6°. In such embodiments, the X-ray mirror20 may be arranged such that the generated EUV light may be incident onthe portion 45 of the mask 40 at an angle of, e.g., 6°, with respect toa normal line of the mask 40. Instead of the X-ray mirror 20, thezoneplate lens 30 may be arranged such that the EUV light reflected bythe X-ray mirror 20 may be incident on the portion 45 of the mask 40 atan angle of 6° with respect to the normal line of the mask 40.

In some embodiments, the apparatus for measuring an aerial image mayinclude a movable unit 35 arranged adjacent, e.g., under, the mask 40.The movable unit 35 may move the mask 40 along an x-axis and/or y-axisdirection, and may allow the detector 50 to scan an entire upper surfaceof the mask 40.

FIG. 3A illustrates a schematic diagram of an exemplary embodiment of azoneplate lens 30 a and a detector 50 a employable in an apparatus formeasuring an aerial image, and FIG. 3B illustrates a schematic diagramof an exemplary embodiment of a scanner employable in an apparatus formeasuring an aerial image.

In the exemplary embodiment of an apparatus for measuring an aerialimage illustrated in FIGS. 1 and 2, the mask (see 40 of FIGS. 1 and 2)reflects the EUV light toward the detector (see 50 of FIGS. 1 and 2). Itshould be understood that embodiments are not limited thereto. Forexample, as shown in FIG. 3A, a mask 40 a may transmit EUV light towardthe detector 50 a.

In a EUV scanning process, EUV light may be reflected and/or transmittedby a mask and the reflected/transmitted EUV light may be projected withreduction magnification on a photoresist on a surface of a wafer. Forexample, a size ratio of a pattern formed on a mask, e.g., 40, 40 a, ofa scanner to an entity pattern formed by projecting EUV light on thesurface of the wafer by the scanner may be in range of about 4:1 toabout 5:1. The size ratio of the pattern formed by projecting EUV lightby the scanner, i.e., a reduction ratio may be used to control anumerical aperture of the zoneplate lens, e.g., 30, 30 a, and thedetector, e.g., 50, 50 a. In embodiments, to emulate the pattern formedby projecting EUV light by the scanner, the numerical aperture of thedetector, e.g., 50, 50 a, may be controlled in consideration of anoff-axis degree of the scanner.

Referring to FIG. 3A, a relationship between the zoneplate lens 30 a,the detector 50 a, and the scanner may be represented by Equation 1.

$\begin{matrix}{{{NA}_{zoneplate} = \frac{{NA}_{scanner}}{n}}{{NA}_{detector} = {\frac{{NA}_{scanner}}{n}*\sigma}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$In Equation 1, NA_(zoneplate) denotes the numerical aperture (NA) of thezoneplate lens 30 a, NA_(detector) denotes the NA of the detector 50 a,and NA_(scanner) denotes the NA of the scanner, σ denotes the off-axisdegree of the scanner, and n denotes a reduction magnification of thescanner.

Referring to FIG. 3B, a relationship between the NA_(scanner) and σ maybe represented by Equation 2.

$\begin{matrix}{{{NA}_{scanner} = {\sin\; y}}{\sigma = \frac{\sin\; x}{\sin\; y}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$In Equation 2, x denotes an angle formed by EUV light focused by afocusing lens 41 of the scanner with respect to a center of the focusinglens 41 and y denotes an angle formed by EUV light that is reflectedtoward a focusing mirror 42 by the mask 40 with respect to a center ofthe focusing mirror 42.

More particularly, e.g., in an exemplary embodiment of the mask 40 a,the zoneplate lens 30 a and the detector 50 a of FIG. 3A, a size ratioof a pattern formed in the mask 40 a to the entity pattern formed byfocusing and projecting EUV light on a surface of the wafer by thescanner may be 4:1. In such an embodiment, because the reductionmagnification of the scanner is 4, NA_(scanner) and σ may be calculatedusing Equation 2, and the zoneplate lens 30 a and the detector 50 a maydesigned such that Equation 1 in which NA_(zoneplate)=NA_(scanner)/4 andNA_(detector)=NA_(scanner)/4*σ is satisfied.

Thus, referring, e.g., to FIG. 3A, embodiments of an apparatus formeasuring an aerial image may be formed in consideration of a coherentEUV light, an incident angle 25 of the coherent EUV light that is set tobe incident to a portion of the mask 40 a at a same angle as an incidentangle of a scanner with respect to a normal line of the mask 40 a, andnumerical apertures of the zoneplate lens 30 a and the detector 50 a(NA_(zoneplate) and NA_(detector)) which may be set to satisfyEquation 1. Embodiments of the apparatus for measuring an aerial imageformed as described above may substantially and/or perfectly emulate thenumerical aperture and off-axis degree of a scanner. Thus, when the mask40 a is a reflective EUV mask including an upper portion having acircuit pattern, an aerial image that is identical to a circuit patternprojected, by the scanner, on a photoresist of a wafer may be measuredusing embodiments of an apparatus for measuring an aerial imageincluding one or more features described herein.

FIG. 4A illustrates a schematic diagram of an exemplary embodiment ofthe computing unit 60 employable in the apparatus of FIG. 1, and FIG. 4Billustrates a schematic diagram of an exemplary embodiment of a drivingprocess of the detector 50 and the computing unit 60 employable in theapparatus of FIG. 1.

Referring to FIG. 4A, the computing unit 60 may include a control unit70, a storage unit 80, and an output unit 90. When EUV light 100 isreflected by the portion 45 of the mask 40 and energy of the reflectedEUV light 100 is detected by the detector 50, an energy information 200may be transferred to the control unit 70. The control unit 70 mayreconstruct an image using the transferred energy information 200. Thereconstructed image information 300 may be represented on a scale of 0to 1 corresponding to the light intensity of the EUV light 100. Thereconstructed image information 300 may be transferred to the storageunit 80. The storage unit 80 may store the reconstructed imageinformation 300 about the portion 45 of the mask 40 in the form of amatrix data 400. For example, if the mask 40 is divided in regions(5×5), reconstructed image information about the respective regions maybe stored using a matrix data (5×5). The control unit 70 may load thematrix data 400 stored in the storage unit 80. The control unit 70 maytransmit the matrix data 400 to the output unit 90. The output unit 90may output the aerial image of the mask 40 using the transmitted matrixdata 400.

More particularly, referring to FIG. 4B, the mask 40 may be divided,e.g., into 25 regions. Further, e.g., EUV light may be reflected in afirst region 1, and the detector 50 may sense an energy of the reflectedEUV light and transmit first energy information 110 to the computingunit 60. Using the transmitted first energy information 110, the controlunit 70 of the computing unit 60 may reconstructs the image of the firstregion 1 of the mask 40. Reconstructed first image information 110′ ofthe first region may be transmitted to the storage unit 80. The storageunit 80 may store the reconstructed first image information 110′ in aregion (1×1) of the matrix data 400 (5×5). Then, the movable unit 35 maymove the mask 40 in a −x-axis direction.

EUV light may then be reflected in a second region 2 of the mask 40, andthe detector 50 may sense an energy of the reflected EUV light and maytransmit second energy information 120 to the computing unit 60. Usingthe transmitted second energy information 120, the control unit 70 ofthe computing unit 60 may reconstruct the image of the second region 2of the mask 40. Reconstructed second image information 120′ of thesecond region may be transferred to the storage unit 80. The storageunit 80 may store the reconstructed second image information 120′ in aregion (1×2) of the matrix data 400. Then, the movable unit 35 may movethe mask 40 in the −x-axis direction.

In the exemplary embodiment illustrated in FIG. 4B, such operation maybe repeated until an image of a fifth region of the mask 40 isreconstructed and the reconstructed fifth image is stored in the matrixdata 400 of the storage unit 80. Then, the movable unit 35 may move themask 40 in a +y-axis direction. EUV light may then be reflected in asixth region 6 of the mask 40, and sixth energy information 160 may begenerated by the detector 50. The sixth energy information 160 may betransmitted to the computing unit 60. The transmitted sixth energyinformation 160 may be reconstructed in the control unit 70, andreconstructed sixth image information 160′ of the sixth region may betransmitted to the storage unit 80 and stored in a region (2×5) of thematrix data 400.

The images of the 25 regions of the mask 40 may be reconstructed bymoving the mask 40 in the x-axis or y-axis, and respectively storing thereconstructed images in the matrix data 400 of the storage unit 80. Whenthe reconstructed image information about the entire region of the mask40 is stored in the storage unit 80, the control unit 70 may load thematrix data 400 of the storage unit 80. The output unit 90 may thenoutput the aerial image of the mask 40 using the matrix data 400 loadedfrom the control unit 70.

FIG. 5 illustrates a perspective view of an exemplary embodiment of theEUV mask 40 including a mask pattern 500 and a defect 600 thereon. FIG.6 illustrates an exemplary output image corresponding an aerial image ofthe mask 40 of FIG. 5, which may be output by the output unit 90 (seeFIG. 4B) in the form of light and darkness using the values of thetransmitted matrix data (see 400 a of FIG. 5). FIG. 7 illustratesexemplary cross-sectional aerial images of diagrams that may be outputby the output unit 90 (see FIG. 4B), wherein the cross-sections aretaken along lines a-a′, b-b′, and c-c′ of FIG. 5. Referring to FIGS. 5,6 and 7, operations of the control unit for reconstructing an image andthe output unit 90 for outputting an aerial image of the mask 40 aredescribed below. Based on the reconstructed image, it may be determinedwhether a defect, e.g., 600, exists in a mask pattern 500.

Referring to FIG. 5, the exemplary embodiment of the mask 40 may bedivided into 36 regions and the images of the 36 regions of the mask 40may be reconstructed by moving the mask 40 in the x-axis and y-axisdirections. The reconstructed respective image information may be storedin the matrix data 400 a (3×12) of the storage unit 80 (See FIG. 4B).

In the exemplary embodiment of FIG. 5, with regard to a first region 1of the mask 40, energy of most and/or all incident EUV light may bereflected from the first region 1 and may be sensed by the detector,e.g., 50 of FIG. 4B. Thus, in a corresponding region (1×1) of the matrixdata 400 a, corresponding image information reconstructed by the controlunit 70 (FIG. 4B) based on a first energy information generated by thedetector 50 with regard to the first region 1 may have a value of ‘1’.More particularly, the control unit 70 may transmit the value ‘1’ to thestorage unit 80 and the value ‘1’ may be stored in the correspondingregion (1×1) of the matrix data 400 a.

The movable unit 35 may then move the mask 40 in the −x-axis direction.EUV light may then be irradiated to a second region 2 of the mask 40.Referring to FIGS. 4B and 5, with regard to the second region 2, energyof most and/or all incident EUV light may be reflected from the secondregion 2 and may be sensed by the detector 50. Thus, in a correspondingregion (1×2) of the matrix data 400 a, corresponding image informationreconstructed by the control unit 70 based on a second energyinformation generated by the detector 50 with regard to the secondregion 2 may have a value of ‘1’. More particularly, the control unit 70may transmit the value ‘1’ to the storage unit 80 and the value ‘1’ maybe stored in the corresponding region (1×2) of the matrix data 400 a.

The movable unit 35 may then move the mask 40 in the −x-axis direction.EUV light may then be irradiated to a third region 3 of the mask 40.Referring to FIGS. 4B and 5, with regard to the third region 3, energyof most and/or all incident EUV light may be reflected from the thirdregion 3 and may be sensed by the detector 50. Thus, in a correspondingregion (1×3) of the matrix data 400 a, corresponding image informationreconstructed by the control unit 70 based on a third energy informationgenerated by the detector 50 with regard to the third region 3 may havea value of ‘1’. More particularly, the control unit 70 may transmit thevalue ‘1’ to the storage unit 80 and the value ‘1’ may be stored in thecorresponding region (1×3) of the matrix data 400 a.

The movable unit 35 may move the mask 40 in the −x-axis direction. EUVlight may then be irradiated to a fourth region 4 of the mask 40.Referring to FIGS. 4B and 5, with regard to the fourth region 4, energyof about 50% of all incident EUV light may be absorbed by the maskpattern 500 and about 50% may be reflected from the fourth region 4, andmay be sensed by the detector 50. Thus, in a corresponding region (1×4)of the matrix data 400 a, corresponding image information reconstructedby the control unit 70 based on a fourth energy information generated bythe detector 50 with regard to the fourth region 4 may have a value of‘0.5’. More particularly, the control unit 70 may transmit the value‘0.5’ to the storage unit 80 and the value ‘0.5’ may be stored in thecorresponding region (1×4) of the matrix data 400 a.

The movable unit 35 may move the mask 40 in the −x-axis direction. EUVlight may then be irradiated to a fifth region 5 of the mask 40.Referring to FIGS. 4B and 5, with regard to the fifth region 5, energyof about 100% of all incident EUV light may be absorbed by the maskpattern 500 and about 0% may be reflected from the fifth region 5, andmay be sensed by the detector 50. Thus, in a corresponding region (1×5)of the matrix data 400 a, corresponding image information reconstructedby the control unit 70 based on a fifth energy information generated bythe detector 50 with regard to the fifth region 5 may have a value of‘0’. More particularly, the control unit 70 may transmit the value ‘0’to the storage unit 80 and the value ‘0’ may be stored in thecorresponding region (1×5) of the matrix data 400 a.

The operations described above may be repeated until EUV light isirradiated to each of a sixth through twelfth regions of the mask 40,and the corresponding energy information of the EUV light isreconstructed. In such embodiments, at this stage, the image informationof the first through twelfth regions of the mask 40 may be stored inregions (1×1, 1×2, 1×12) of the matrix data 400 a.

Then, in such embodiments, e.g., the movable unit 35 may move the mask40 in the +y-axis direction. EUV light may then be irradiated to a13^(th) region 13 of the mask 40. Referring to FIGS. 4B and 5, withregard to the 13^(th) region 13, energy of about 50% of all incident EUVlight may be absorbed by the mask pattern 500 and about 50% may bereflected from the 13^(th) region 13, and may be sensed by the detector50. Thus, in a corresponding region (2×12) of the matrix data 400 a,corresponding image information reconstructed by the control unit 70based on a thirteenth energy information generated by the detector 50with regard to the thirteenth region 13 may have a value of ‘0.5’. Moreparticularly, the control unit 70 may transmit the value ‘0.5’ to thestorage unit 80 and the value ‘0.5’ may be stored in the correspondingregion (2×12) of the matrix data 400 a.

The movable unit 35 may then move the mask 40 in the +x-axis direction.Likewise, EUV light may be irradiated to 14^(th) through 24^(th) regionsof the mask 40 and the control unit 70 may respectively reconstructenergy information of EUV light reflected from each of the respectiveregions. The reconstructed 14^(th) through 24^(th) image information maybe stored in regions (2×11, 2×10 through 2×1) of the matrix data 400 a.

Further, e.g., with regard to the 17^(th) region 17, a portion of EUVlight may be absorbed by the defect 600 of the mask pattern 500.Referring to FIGS. 4B and 5, when EUV light is irradiated to the 17^(th)region 17 of the mask 40, Referring to FIGS. 4B and 5, energy of about20% of all incident EUV light may be absorbed by the defect 600 andabout 80% may be reflected from the 17^(th) region 17, and may be sensedby the detector 50. Thus, in a corresponding region (2×8) of the matrixdata 400 a, corresponding image information reconstructed by the controlunit 70 based on a seventeenth energy information generated by thedetector 50 with regard to the seventeenth region 17 may have a value of‘0.8’. More particularly, the control unit 70 may transmit the value‘0.8’ to the storage unit 80 and the value ‘0.8’ may be stored in thecorresponding region (2×8) of the matrix data 400 a.

When the respective image information about the 13^(th) through 24^(th)regions of the mask 40 is reconstructed and stored in the correspondingregions (2×9 through 2×1) the matrix data 400 a of the storage unit, themovable unit 35 may move the mask 40 in the +y-axis direction. EUV lightmay then be irradiated to 25^(th) through 36^(th) regions of the mask 40and the control unit 70 may reconstruct respective energy information ofEUV light reflected from the respective regions. The reconstructed25^(th) through 36^(th) image information may be stored in regions (3×1through 3×12) of the matrix data 400 a of the storage unit 80.

The matrix data 400 a stored in the storage unit 80 may be transmittedto the output unit 90. The output unit 90 may output the correspondingaerial image in the form of, e.g., light and darkness and/or in the formof a cross-sectional view based on the values of the matrix data 400 a.

Referring to FIG. 6, the output unit 90 may output the correspondingaerial image of the mask 40 in the form of light and dark regions, e.g.,36 regions, based on the respective values of the transmitted matrixdata (see 400 a of FIG. 5). For example, according to the values of thematrix data 400 a, 0 may be output as black, 1 may be output as white,0.5 may be output as gray, and 0.8 may be output as gray, with darknessof gray decreasing as the value approaches 1. When the aerial image ofthe mask 40 is output according to the corresponding matrix data (see400 a of FIG. 5), it may be determined whether a defect, e.g., defect600, has occurred or not. In the exemplary embodiment of FIGS. 5-7, thedefect 600 is present.

Referring to the exemplary aerial image of FIG. 6, with regard to theaerial image of the exemplary mask 40 illustrated therein, the firstthrough 12^(th) regions repeat a pattern unit 510 (1-1-1-0.5-0-0.5), andthus it may be expected that scanning can be performed without anyproblem. The 19^(th) through 24^(th) (14→24) regions also have thepattern unit 510, and the 25^(th) through 36^(th) regions have two ofthe pattern unit 510, and thus it may be expected that scanning can beperformed without any problem. However, the 13^(th) through 18^(th)regions have a defective pattern unit 520 (1-0.8-1-0.5-0-0.5) includinga defect 550, corresponding to the defect 600 (see FIG. 5) of the17^(th) region 17. Thus, it may be expected that a defect may be formedin a photoresist when developed after scanning.

Referring to FIG. 7, the output unit 90 (see FIG. 4B) may output aerialimages of the mask 40 based on the values of the correspondingtransmitted matrix data (see 400 a of FIG. 5). In FIG. 7, the exemplaryaerial images are cross-sectional views along lines a-a′, b-b′, and c-c′of FIG. 5. For example, the output unit 90 may output the aerial imageof a portion of the mask taken along line a-a′ based on values ofregions along a first row of the matrix data (see 400 a of FIG. 5).Likewise, the aerial images of portions of the mask taken along linesb-b′ and c-c′ may be output based on values of the second and third rowsof the matrix data (see 400 a of FIG. 5).

Referring to FIGS. 5, 6 and 7, the a-a′ cross-section (first through12^(th) regions), and the c-c′ cross-section (25^(th) through 36^(th)regions) may each include two of a pattern unit 610 (1-1-1-0.5-0-0.5),and thus, it may be expected that scanning may be performed without anyproblem. With regard to the b-b′ cross-section (13^(th) through 24^(th)regions), the 19^(th) through 24^(th) regions may include the patternunit 610 (1-1-1-0.5-0-0.5), and thus, it may be expected that scanningmay be performed without any problem. However, the 13^(th) through18^(th) regions may include a defective pattern unit 620(1-0.8-1-0.5-0-0.5) including a defect 650 of the 17^(th) region, andthus, it may be expected that a defect may be formed in a photoresistdeveloped after scanning.

In some embodiments, the output unit 90 may output aerial images thatare symmetric to the aerial images described above with respect to anx-axis, and thus, an expected image of a photoresist pattern on a waferthat is developed after scanning, not the aerial image of the mask, maybe obtained.

FIGS. 8A and 8B each illustrate a cross-sectional view of an imageprojected onto a photoresist and a corresponding aerial image of a maskreconstructed by an output unit of an apparatus for measuring an aerialimage according to another embodiment of the inventive concept, whereinthe aerial image shows a cross-sectional view of the mask.

Referring to FIG. 8A, in an exemplary embodiment, NA_(scanner) is 0.25and G is 0. Thus, the zoneplate lens 30 and the detector 50 (see, e.g.,FIG. 1) of the apparatus for measuring an aerial image may be designedin consideration of numerical apertures obtained using Equation 1(NA_(zoneplate)=0.25/4=0.0625, and NA_(detector)=0).

Referring to FIG. 8B, in an other exemplary embodiment, NA_(scanner) is0.25 and σ is 1. Thus, the zoneplate lens 30 and the detector 50 of theapparatus for measuring an aerial image may be designed in considerationof numerical apertures obtained using Equation 1(NA_(zoneplate)=0.25/4=0.0625, NA_(detector)=0.0625).

Referring to FIGS. 8A and 8B, it may be seen that images 800 a and 800 bprojected onto a respective photoresist are identical to aerial images810 a and 810 b that are output using the apparatus (see, e.g., FIG. 1)for measuring an aerial image designed according to Equation 1, whereinthe aerial images 800 a, 800 b, 810 a and 810 b illustratecross-sectional views. Thus, an apparatus for measuring an aerial imageemploying one or more features described herein may emulate an imageprojected on a photoresist based on the numeric aperture and off-axisdegree of a scanner.

FIG. 9A illustrates an exemplary mask pattern 900 that includes a defect910 and from which energy information may be obtained and supplied tothe output unit of FIG. 4B. FIG. 9B illustrates an exemplary lightaerial image, which may be output from, e.g., the output unit 90 of FIG.4B, and FIG. 9C illustrates an exemplary dark aerial image, which may beoutput from the output unit 90 of FIG. 4B.

Referring to FIG. 9A, in an exemplary embodiment, NA_(scanner) is 0.25,and, according to Equation 1, NA_(zoneplate)=NA_(scanner)/4=0.0625. Inthe exemplary embodiment, because σ is 0.5,NA_(detector)=NA_(scanner)/4*σ=0.03125. As described above with regardto Equation 1 and Equation 2, in embodiments, a zoneplate lens, e.g., 30of FIG. 1, and a detector, e.g., 50 of FIG. 1, may be designed accordingto NA_(zoneplate) and NA_(detector). In the exemplary embodiment of FIG.9A, the mask 900 including the defect 910 having a size of 40 nm may bemeasured using an embodiment of apparatus for measuring an aerial imageincluding one or more features described herein.

Referring to FIGS. 9B and 9C, in corresponding light and dark aerialimages of the mask 900, the defect 910 may appear white and black,respectively, a corresponding region 920 of the output image. In theexemplary embodiment of FIGS. 9A, 9B and 9C, the defect 910 affects 10%or more of the aerial image intensity. In some embodiments, whether adefect may be detected may be based on an extent of the defect. That is,e.g., in some embodiments, only defects affecting more than apredetermined amount of an aerial image intensity may be detected. Inthe exemplary embodiment of FIGS. 9A, 9B, and 9C, a defect affecting 10%or more of the aerial image intensity may be flagged. Thus, the defect910 may be flagged as a defect, and the mask pattern 900 may becorrected, e.g., removed/filled, before the mask may be scanned, e.g.,during a semiconductor fabrication process. That is, by employing amethod or apparatus for detecting a defect accordingly a defect of amask may be sensed and removed before the scanning.

FIG. 10 illustrates a flowchart of an exemplary embodiment of a methodof measuring an aerial image.

Referring to FIG. 10, EUV light may be generated (S100), and thegenerated EUV light may be reflected by an X-ray mirror (S200). TheX-ray mirror may be arranged such that the EUV light is incident on aportion of a mask at an angle of about 4° to about 8° with respect to anormal line of the mask. The reflected EUV light may be transmitted by azoneplate lens (S300). The zoneplate lens may be arranged such that theEUV light is incident on a portion of the mask at an angle of about 4°to about 8° with respect to the normal line of the mask. The EUV lightfocused on the portion of the mask may be reflected by the maskincluding a reflective material (S400). The detector may sense energy ofthe EUV light reflected by the mask (S500). In embodiments, thezoneplate lens and the detector may be formed such that Equation 1 issatisfied. The sensed energy may be reconstructed in the form of imageinformation represented as a numeric value, the numerical value of theimage information may be stored in a matrix data of a storage unit(S600). Then, a movable unit may move the mask in an x-axis or y-axisdirection (S700), and the operations described above may be repeatedlyperformed. When image information of an entire region of the mask isstored in the matrix data, the aerial image of the mask may be output byusing the matrix data (S800).

It will also be understood that when an element is referred to as being“between” two elements, it can be the only element between the twoelements, or one or more intervening elements may also be present. Likereference numerals refer to like elements throughout the specification.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the inventiveconcept. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present inventive concept.

Embodiments are described herein with reference to cross-sectionillustrations that are schematic illustrations of idealized embodimentsof the present inventive concept. As such, variations from the shapes ofthe illustrations as a result, for example, of manufacturing techniquesand/or tolerances, are to be expected. Thus, the illustrations shouldnot be construed as limited to the particular shapes of regionsillustrated therein, but are to include deviations in shapes thatresult, for example, from manufacturing. For example, in the drawingsused to describe the exemplary embodiments, the shapes of the respectivecomponents are for illustrative purposes only. The respective componentsmay have various other shapes.

Exemplary embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense only and not for purpose of limitation.Accordingly, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made without departingfrom the spirit and scope of the present invention as set forth in thefollowing claims.

1. A method of measuring an aerial image of a pattern corresponding to asemiconductor pattern to be formed by scanning the pattern using ascanner, the method comprising: generating an extreme ultra-violet (EUV)light using a light source; reflecting the generated EUV light using amirror; focusing the reflected EUV light on a first portion of an EUVmask through a zoneplate lens, such that an incidence angle of the EUVlight on the EUV mask is other than zero with respect to a normal to theEUV mask; sensing energy of the EUV light reflected from the EUV maskusing a detector; focusing the reflected EUV light on a second portionof an EUV mask using the zoneplate lens; and sensing energy of the EUVlight reflected from the second portion of the EUV mask using thedetector.
 2. The method as claimed in claim 1, wherein focusing thereflected EUV light includes using a zoneplate lens having a numericalaperture based on parameters of a scanner used to form a pattern throughthe EUV mask, the parameters of the scanner including a numericalaperture and a reduction magnification.
 3. The method as claimed inclaim 2, wherein NA_(detector)=NA_(scanner)/n, where NA_(detector)denotes a NA of the detector, NA_(scanner) denotes a NA of the scanner,and n denotes a reduction magnification of the scanner.
 4. The method asclaimed in claim 1, wherein focusing the reflected EUV light on theportion of the EUV mask includes focusing the EUV light at a same angleas an angle at which a scanner will be disposed with respect to thenormal to the EUV mask.
 5. The method as claimed in claim 1, wherein thezoneplate lens is disposed between the EUV mask and the mirror.
 6. Themethod as claimed in claim 1, wherein the aerial image of the EUV maskis made based on sensed energy of the EUV light reflected from portionsof the EUV mask.
 7. The method as claimed in claim 1, further comprisingconverting the sensed energy into image information and storing theimage information.
 8. The method as claimed in claim 7, furthercomprising outputting an aerial image of the pattern of the EUV maskbased on the stored information.
 9. The method as claimed in claim 7,further comprising: moving the EUV mask in an x-axis direction and/ory-axis direction by a movable unit, wherein an EUV light is focused on asecond portion of the EUV mask through the zoneplate lens.
 10. Themethod as claimed in claim 9, wherein the zoneplate lens is disposedbetween the movable unit and the mirror.
 11. The method as claimed inclaim 1, wherein generating extreme ultraviolet light includesgenerating a high power femtosecond laser beam.
 12. The method asclaimed in claim 1, wherein the mirror is an X-ray mirror comprising amulti-layer structure including at least one molybdenum layer and atleast one silicon layer, which are alternately arranged.
 13. A method ofpatterning a semiconductor device, the method comprising: emitting afirst EUV light from a first light source through a zoneplate lenstoward a first portion of a photomask having circuit patterns thereon;detecting with a detector energy of the first EUV light reflected fromthe first portion of the photomask to store image information of thecircuit patterns; emitting the first EUV light from the first lightsource through the zoneplate lens toward a second portion of thephotomask, detecting with the detector energy of the first EUV lightreflected from the second portion of the photomask to store imageinformation of the circuit patterns; emitting a second EUV light towardthe photomask through a focusing lens; and patterning a surface of asemiconductor wafer using the second EUV light reflected from thephotomask.
 14. The method as claimed in claim 13, wherein emitting thefirst EUV light through the zoneplate lens includes using a zoneplatewith a numerical aperture based on parameters of a scanner used to forma pattern through the EUV mask, the parameters of the scanner includinga numerical aperture and a reduction magnification.
 15. The method asclaimed in claim 14, wherein NA_(detector)=NA_(scanner)/n, whereNA_(detector) denotes a NA of the detector, NA_(scanner) denotes a NA ofthe scanner, and n denotes a reduction magnification of the scanner. 16.The method as claimed in claim 13, wherein the zoneplate lens is adaptedto focus the EUV light on a portion of the EUV mask at a same angle asan angle at which the scanner will be disposed with respect to a normalline of the EUV mask.
 17. A method of patterning a semiconductor device,the method comprising: emitting from a light source a first EUV lightthrough a zoneplate lens toward a first portion of a photomask havingcircuit patterns thereon; detecting with a detector energy of the firstEUV light reflected from the first portion of the photomask to storeimage information of the circuit patterns; emitting from the lightsource the first EUV light through the zoneplate lens toward a secondportion of the photomask; detecting with the detector energy of thefirst EUV light reflected from the second portion of the photomask tostore image information of the circuit patterns; and performing an EUVscanning process by projecting a second EUV light reflected from thephotomask on a surface of a semiconductor wafer.
 18. The method asclaimed in claim 17, wherein numerical aperture of the zoneplate lens isbased on parameters of a scanner used to form a pattern through the EUVmask, the parameters of the scanner including a numerical aperture and areduction magnification.
 19. The method as claimed in claim 18, whereinNA_(detector)=NA_(scanner)/n, where NA_(detector) denotes a NA of thedetector, NA_(scanner) denotes a NA of the scanner, and n denotes areduction magnification of the scanner.
 20. The method as claimed inclaim 17, wherein the zoneplate lens is adapted to focus the EUV lighton a portion of the EUV mask at a same angle as an angle at which thescanner will be disposed with respect to a normal line of the EUV mask.